Water - EQ1 - Flashcards
Where did earths water come from
- carbonaceous chondrite meteorite
Define systems approach
- the hydrological cycle is studied by looking at the balance of inputs & how water is moved between stores by flows
Define stores
- reservoirs where water is held e.g oceans
Define fluxes
- rate of flow between the stores
Define processes
- physical mechanisms that drive the fluxes of water between the stores
Define cryosphere
- areas of the earth where water is frozen into snow or ice
Define transpiration
- the loss of water from vegetation into the atmospphehre involving a change from a liquid to a gas
Define blue water
- water is in rivers, streams, lakes & groundwater in liquid form
- visible part of the hydrological cycle
Define green water
- water stored in the soil & vegetation
- invisible part of the hydrological cycle
Define fossil water
- ancient, deep groundwater, from pluvial wetter periods
Define ground water flow
- the slow transfer of percolated water underground through pervious o rporous rocks
Define groundwater recharge
- a hydrological process where water percolates downward from surface water to groundwater
define renewable water
- water that is replenished by the hydrological cycle within human time scales
define non-renewable water
- groundwater bodies (deep aquifers) that have a negligible rate of recharge on the human timescale
define pervious rock
- allows water to pass through it due to cracks or defects
define porous rock
- allows water to flow through the pores
define residence times
- the average time a water molecule will spebd in a reservoir or store
The global hydrological cycle is the…
…circulation of water around the earth
Why is the global hydrological cycle a closed system
- there is a fixed amount of water in the earth’s atmosphere - estimated at 1385 million km^3
- it does not have any external inputs or outputs, so this volume of water is constant & finite
- water exists in different states within a closed system
- the amount held in each state can vary for physical & human reasons
The cycle is driven by solar & gravitational potential energy, what does this mean
- solar energy causes the water to change state (gas, liquid, solid)
- when the subject is above the earths surface it has GPE, causing rivers to flow downhill and precipitation to fall to the ground
- the energy is converted into kinetic energy as water moves through the system
List 6 water stores
- oceans
- ice caps
- ground water
- rivers & lakes
- soil moisture
- atmospheric moisture
Distribution of the earth’s water
freshwater v saline (saltwater)
- saline - 97.5%
- freshwater - 2.5%
Distribution of freshwater
What can fresh water be divided into
- ice caps & glaciers - 68.7%
- groundwater - 30.1%
- surface water - 0.3%
Distribution of fresh surface water
What can surface water be divided into
- 52% - lakes
- 38% - soil moisture
- 8% - atmospheric water vapour
- 1% - rivers
- 1% - accessible water in plants
What is the global water budget
- the annual balance of water fluxes (flows)
- & the size of the water stores
Describe how fluxes balance the precipitation cycle
- more water falls as precipitation to the land masses than is evaporated
- the balance is made up by river run off - excess water on the land is returned to the sea
- if the precipitation & evaporation budget did not work in this way, the land masses would progressively dry up, & oceans would progressively gain all of the world’s water
What is the residence time of oceans
- 3,600 years
What is the residence time of ice caps
- 15,000 years
What is the residence time of groundwater
- up to 10,000 years for deep ground water
- 100-200 years for shallow
What is the residence time of rivers & lakes
- 2 weeks to 10 years, 50 years for very largescale
What is the residence time of soil moisture
- 2-50 weeks
What is the residence time of atmospheric moisture
- 10 days
What is so critical about the global water budget for humans
- accessible surface water is a mere 1% of all the world’s freshwater, and this is the major source of water for human use
- the smallness of this figure emphasises the important point that water is not the abundant resource,, it is a scarce resource needing careful management
define drainage basin
- area of land drained by a river
- they are sometimes freffered to as a ctahcment area
A drainage basin is a…..within the global hydrological cycle, which is …. with external inputs & outputs
- subsystem
- open
how can drainage basins vary in size
- they can be from a small scale stream & small rivers nestle within the drainage basisns of larger rivers
Define watershed
- the edge of high land surrounding a drainage basin, it marks the boundary between 2 drainage basins
Define source
- the beginning or start of a river
Define confluence
- the point at which 2 rivers or streams join
Define tribituary
- a stream or smaller river which joins a larger stream or river
Define mouth
- the point at which the river meets the sea
What are the 3 features of the water cycle system
- inputs
- flows (processes)
- outputs
Define inputs
- the movement of matter into a system, in the hydrological cycle closed system,
- this is an internal movement into a store only, e.g precipitation
Define outputs
- The movement of matter out of a system
- in the hydrological cycle closed system, this is an internal movemen,t only out of a store e.g evaporation
Define flows
- The amount of matter (or energy) transferred from one place to another
Define stores
- Where matter (or energy) is kept for a relatively long period of time
Define solar energy
- Heat energy from the Sun causes changes in the state of water and drives some of the processes within the hydrological cycle, such as evaporation and wind direction
Define Gravitational Potential energy
- The mass of the Earth exerts a pull on water, causing water to fall as precipitation and rivers to flow downhill back to the ocean (the main store)
define interception
- the retention of water by plants and soils which is subsequently evaporated or absorbed by the vegetation
define infiltration
- the process by which water soaks into, or is absorbed by, the soil
define percolation
- similar to infiltration, but a deeper transfer of water into permeable rocks
define throughflow
- the lateral transfer of water downslope through the soil
define groundwater flow
the very slow transfer of percolated water through pervious (permeable) or porous rocks
define surface runoff
- the movement of water that is unconfined by a channel across the surface of the ground a.k.a. overland flow
define channel flow
takes over as soon as the water enters a river or stream; the flow is confined within a channel
what are the 3 types of precipitation patterns
- orographic (relief)
- frontal
- convectional
what is orographic (relief) rainfall
- caused when humid air is forced to rise over mountains
- when the air cools at higher altitude, moisture condenses, forms clouds and droplets of water which then fall due to gravity
- most rain falls on the slopes facing the wind direction and tops of the mountains, with drier air on the other side (lee) so less rain falls (rain shadow).
what is frontal rainfall
- caused when warm humid air is forced to rise at a warm front or cold front, usually as part of a low pressure system (depression)
- the air cools, condensation takes place, clouds of water droplets form which is followed by rain
what is convectional rainfall
- caused when the ground and lower atmosphere are heated by the Sun’s energy causing rising thermals of air
- humidity in the air condenses when it cools at higher altitude, forms towering cumulo-nimbus clouds, often followed by intense heavy rainfall (thunderstorms)
define evaporation
the process by which moisture is lost directly into the atmosphere from water surfaces, soil and rock
define transpiration
- the biological process by which water is lost from plants through minute pores and transferred to the atmosphere
what is a different word for channel flow
discharge
define discharge
- Runoff moves to the lowest points in a landscape, where it collects to form a linear body of water flowing over the ground
- The larger the amount of water, the larger the discharge (cubic metres per second)
- It increases with amount of rainfall or snow melt
Describe the physical factors affecting the drainage basin cycle
Relief
- Largely affects the relative importance of the different flows within the system (of these flows perhaps the most important is surface runoff)
- Relief can impact on the amount of precipitation
- Slopes can affect the amount of runoff
Describe the physical factors affecting the drainage basin cycle
Climate
- Mainly impacts on the inputs and outputs
- influencing the type and amount of precipitation overall and the amount of evaporation (i.e. the major inputs and outputs)
- impact on vegetation type
Describe the physical factors affecting the drainage basin cycle
Soils
- Largely affect the relative importance of the different flows within the system (of these flows perhaps the most important is surface runoff)
- Soils determine the amount of infiltration and throughflow,
- & indirectly, the type of vegetation
Describe the physical factors affecting the drainage basin cycle
Geology
- Largely affects the relative importance of the different flows within the system (of these flows perhaps the most important is surface runoff)
- can impact on subsurface processes such as percolation and groundwater flow (and, therefore, on aquifers)
- Indirectly, geology affects soil formation
Describe the physical factors affecting the drainage basin cycle
Vegetation
- Largely affects the relative importance of the different flows within the system (of these flows perhaps the most important is surface runoff)
- The presence or absence of vegetation has a major impact on the amount of interception, infiltration and occurrence of overland flow, as well as on transpiration rates
Describe the human factors affecting the drainage basin cycle
What is Cloud Seeding
- the attempt to change the amount or type of precipitation by dispersing substances into the air that serve as cloud condensation nuclei
Describe the human factors affecting the drainage basin cycle
How effective is cloud seeding
- new technology & research claims to have produced reliable results that make cloud seeding a dependable & affordable water-supply practise for many regions,
- but its effectiveness is still being debated
Describe the human factors affecting the drainage basin cycle
Give an example of cloud seeding being used
- China used Cloud Seeding in Beijing just before the 2008 Olympic Games to create rain to clear the air of pollution
Describe the human factors affecting the drainage basin cycle
Urbanisation
- creates impermeable surfaces that reduce infiltration & increase surface runoff & throughflow through artificial drains
- stream & river discharges often increase rapidly as a result
Describe the human factors affecting the drainage basin cycle
Dam construction
- dams increase surface water stores & evaporation & reduce downstream river discharge
Describe the human factors affecting the drainage basin cycle
give an example of dam construction
- Lake Nasser behind the Aswan Dam in Egypt is estimated to have evaporation losses of 10 to 16 billion cubic metres every year
Describe the human factors affecting the drainage basin cycle
groundwater abstraction
- In some locations, groundwater is abstracted from aquifers faster than iy is replaced, causing reduced groundwater flow & a lower water table
- in others, reduced industrial activity or deforestation has increased ground water storage, increasing the risk of groundwater flooding id the water table reaches the land surface
Describe the human factors affecting the drainage basin cycle
Give examples of how deforestation disrupts the drainage basin cycle by accelerating natural processes
- A lowering of humidities
- Less precipitation
- More surface run off and infiltration
- More evaporation, less transpiration
- More soil erosion and silt being fed into rivers
define water budget
- the annual balance between inputs & outputs, which are influenced by climate
What is the water budget equation
- P=Q+E+-S
- p is precipitation
- q is channel discharge
- e is evapotranspiration
- s is change in storage
water budgets can be used to show … or … balances between … & …
- annual or monthly
- precipitation inputs & evapotranspiration outputs
on what scale can water budgets be calculated
- global
- local
what do water budgets indicate on a national/regional scale
- provide a useful indication of the amount of water available for human use - agriculture, domestic consumption etc
what do water budgets indicate on a local scale
- can inform about available soil water
what is available soil water
- the amount of water that can be stored in the soil & is available for growing crops
why is knowing the available soil water useful
- valauble to users such as farmers, who can use it to identify when irrigation might be required, & how much, to ensure high production of crop yields, securing food & profit
It is most important that soil moisture is high during ….. seasons
- growth
define river regime
- the annual variation in the discharge or flow of a river at a particular point,
- & is usually measured in cumecs
Where is the flow of river regimes from
- much of this flow is not from immediate precipitation,
- sometimes supplied by groundwater
- between periods of rain which feeds steadily into river systems from base water flow
what are the influences on the characteristics a river’s regime
- the amount & type of vegetation cover
- human activities
- the geology & soils, esp permeability & porosity
- the amount, seasonality & intensity of precipitation
- the size of the river & where discharge measurements are taken along its course
- temperature
Explain the factors influencing a river regime’s characteristics
the amount & type of vegetation cover
- wetlands can hold the water & release is very slowlu into the system
Explain the factors influencing a river regime’s characteristics
human activities
- regulate a river’s discharge e.g dam building
Explain the factors influencing a river regime’s characteristics
geology & soils, esp their permeablity & porosity
- groundwater noted in permeable rocks is gradually released into the river as base flow
Explain the factors influencing a river regime’s characteristics
temperatures
- possible meltwater & high rates of evaporation in summer
what is a storm hydrograph
- displays jow discharge changes over a short period of time, e.g one storm or rain event
what does a storm hydrograph show
- shows how discharge (vol of water) rises after a storm reaches its peak & then returns to the normal rate of flow
what would be plotted on a storm hydrograph
- the occurrence of a short period of rain (maybe a heavy shower or storm) over a drainage basin & the subsequent discharge of a river
define peak rainfall
- the time of highest rainfall
define base flow
- the river’s discharge’s normal level
define peak discharge
- the time when the river reaches its highest flow
define rising limb
- the rapid increase in discharge resulting from rainfall, causing surafce run off & then later throughflow
define falling limb
- once the input of rainwater starts to decsrease, so does the discharge, so the river’s level falls
define lag time
- the gap in time between the peak rainfall & peak discharge
define bankful discharge
- the horizontal line marking the level of discharge above which flooding will occur
what are the features of flashy hydrographs
- short lag time
- high peak discharge
- very steep rising limb
what are the features of subdued hydrographs
- long lag time
- low peak discharge
- gently inclined rising limb
…… changes the characteristics of the lands surface, effecting the hydrological cycle & hence the character if storm hydrographs
- urbanisation
Effects of urbanisation on the hydrological cycle
Construction work leads to the removal of the ………….. cover, this exposes the …..
- vegetation
- soil
Effects of urbanisation on the hydrological cycle
Bare soil is eventually replaced by a ………………, both of which are………&……….
- covering of concrete and tarmac
- impermeable & increase surface runoff.
Effects of urbanisation on the hydrological cycle
The …………….. of buildings means that rain falls on roofs and is then swiftly fed into drains by gutters and pipes.
Drains and sewers ……………………. rainwater travels before reaching a stream or river channel.
- high density
- reduce the distance and time
Effects of urbanisation on the hydrological cycle
Urban rivers are often ………………………. to guard against flooding.
When floods occur, they can be more devastating
channelised with embankments
Effects of urbanisation on the hydrological cycle
Bridges can …………………………and act as local dams, thus prompting ………………… floods.
- restrain the discharge of floodwaters
- upstream
synoptic link
why have planners become important players in managing the impacts of urbanisation on flood risk
- many towns and cities are naturally prone to flooding because of their locations
- of the number of people who live in urban places and who therefore need protection
- of the huge amount of money invested in urban property
synoptic link
what actions does flood risk management by the different players involve
strengthening the embankments of streams and rivers
putting in place flood emergency procedures
steering urban development away from high-risk areas such as floodplains
Conditions likely to produce a flashy hydrograph
Drainage basin size
- Small basins: water will reach the channel rapidly, as it has a shorter distance to travel
Conditions likely to produce a flashy hydrograph
Drainage basin shape
- Circular basins: it will take less time for the water to reach the channel, as all the extremities are equidistant from the channel
Conditions likely to produce a flashy hydrograph
Drainage basin relief
- Steep slopes: water flows rapidly downhill and reaches the channel quickly
Conditions likely to produce a flashy hydrograph
Soil type
- Clay soils and thin soils: clay soils have a low porosity and the grains swell when they absorb water, so water infiltrates slowl
- Thin soil becomes saturated quickly
Conditions likely to produce a flashy hydrograph
Rock type
- Impermeable rocks: water cannot percolate into the rock, increasing surface runoff to rivers
Conditions likely to produce a flashy hydrograph
vegetation
- Bare/low density, deciduous in winter, means low levels of interception and more rapid movement through the system
Conditions likely to produce a flashy hydrograph
precipitation intensity
- High intensity: when rain falls faster than the infiltration capacity, surface runoff occurs and transports the water rapidly to the channel
Conditions likely to produce a flashy hydrograph
precipitation duration
- Prolonged: the water table rises and the soil becomes saturated, causing surface runoff, which travels rapidly to the river channel
Conditions likely to produce a flashy hydrograph
snowfall
- Fast snowmelt: meltwater cannot infiltrate into the frozen ground, so it flows rapidly over the surface into the river channel
Conditions likely to produce a subdued hydrograph
drainage basin size
- Large basins: water will take longer to reach the channel as it has a greater distance to travel
Conditions likely to produce a subdued hydrograph
drainage basin shape
- Elongated basins: water will take a long time to reach the channel from the extremities of the drainage basin
Conditions likely to produce a subdued hydrograph
drainage basin relief
- Gentle slopes: water can infiltrate into the ground and travel slowly to the channel through the soil and rock
Conditions likely to produce a subdued hydrograph
soil type
- Sandy soils and thick soils: sandy soils have a high porosity, so the water can infiltrate
- Deep soils allow more infiltration
Conditions likely to produce a subdued hydrograph
rock type
- Permeable rocks: water percolates through pore spaces and fissures into the groundwater store
Conditions likely to produce a subdued hydrograph
vegetation
- Dense, deciduous in summer, means high levels of interception and a slower passage through the system;
- more water lost to evaporation from vegetation surfaces
Conditions likely to produce a subdued hydrograph
precipitation intensity
- Low intensity: water can infiltrate into the soil and then travel slowly through the soil to the river channel
Conditions likely to produce a subdued hydrograph
precipitation duration
- Short duration: most of the water infiltrates into the soil and travels slowly through the soil into the rocks before reaching the channel
Conditions likely to produce a subdued hydrograph
snowmelt
- Slow snowmelt: the ground thaws with the snow, so the meltwater can infiltrate into the soil and rocks before reaching the channel
Describe the location of the Indus river
- The Indus is 3,180 km (1,980 mi)
- Its source is in Tibet and it flows northwest through the disputed region of Kashmir
- Then is bends sharply to the left and flows south through Pakistan before emptying into the Arabian sea near Karachi
Describe the climate of the Indus river
- Cold winter in the Himalaya’s (snow accumulations) leads to glaciers forming
- The melt water from the glaciers feeds the Indus river
- The climate is hotter more tropical conditions as you go into the lower course in Pakistan so evaporation plays a role
- Pakistan is also affected by the monsoon (ITCZ) so there is a marked wet and dry season
Describe the geology of the Indus river
- Sedimentary and metamorphic rocks from the orogeny
- Sand and silt from what was an ocean
Describe the human use of the Indus river
- Sacred to Hindu’s
- Irrigation for agriculture - cotton, sugar cane and wheat
Describe the location of the Amazon river
- The Amazon is 6,500 km (4,000 mi)
- Its source is in Peru and it flows eastwards towards the Atlantic
- It flows through Brazil and enters the sea by the city of Manaus
- The Amazon basin is the largest in the world (7,000,000km*).
Describe the climate of the Amazon river
- Mountainous (Andes) - snowfall and glaciers in winter
- Tropical (equatorial) wet and dry(ish) season
Describe the geology of the Amazon river
- Andes Mountains (bedrock shield) then sedimentary deposits left from the large inland swamp created before the river worked its way through the sandstone barrier in the west of the continent
Describe the human use of the Amazon river
- Fishing
- Transportation of logging/ fruit
Describe the location of the Yukon river
- The Yukon is 3,190 km (1,980 mi)
- Its source is in British Columbia in Canada and it flows northwest through the Canadian territory named after the river (Yukon) and into Alaska (USA)
- It empties into the Bering Sea
Describe the climate of the Yukon river
- Subarctic climate (short warm summers and lengthy cold winters)
- Around White horse the average Jan temp is -31°C and July is 16°C
Describe the geology of the Yukon river
- 600 million years worth of geology
- East = sedimentary deposits from the ancient continental shelf
- West = metamorphic and igneous from the tectonic collision
Describe the human use of the Yukon river
- Transportation in the 1896-1903 Gold rush
- Military bases
- Fisheries (salmon)
Northern Hemisphere Water Budget Case Studies
what are the implications for the hydrological cycle of at least 17% of Amazon forest being lost
- This forest released 20 km3 of water to atmosphere every day, but this amount is now reducing
- Deforested areas are 3°C warmer and much drier than forested areas
- Dry seasons are getting longer, with 21% reduction in rainfall by 2050
Northern Hemisphere Water Budget Case Studies
Describe how water budgets can be influenced by a polar climate such as Northern Canada
- Precipitation low all year, and maximum in summer (July and August = 24 mm).
- Evapotranspiration only between May and September when temperatures are a little higher and plant growth occurs (July peak = 126 mm)
- Soil moisture recharge between September and May, especially with snowmelt, and a surplus at the start of the summer but with a deficit by August
Northern Hemisphere Water Budget Case Studies
Describe how water budgets can be influenced by a temperate climate such the Southern UK
- Precipitation similar all year 50mm per month, with slight summer decrease (May to August)
- Large variations in evapotranspiration: high in July (70 mm) but very low in winter (December = 5 mm), as temperatures are much lower and plant growth ceases.
- Soil moisture deficit in July and August when plants have used the winter surplus
Northern Hemisphere Water Budget Case Studies
Describe how water budgets can be influenced by a tropical climate, such as the Amazon
- ‘Winter’ (November to January) is a period of recharge when precipitation is higher than evapotranspiration
- Highest rainfall in February, and a soil moisture surplus until May
- Evapotranspiration rates similar all year (100 to 150mm) as average temperature is always about 25°C
- Rainfall much lower from May to November and below evapotranspiration rates, so with plant use, there is a soil moisture deficit by Oct
What are the 3 ways water from a drainage basin is transferred
- directly into the channel - not much
- surface flow - most often
- infiltration - through & base flow
What does the soil water budget depend on
- soil depth
- type
- texture
- permeability
What are the key points to mention when describing hydrographs
- steepness of the rising limb & falling limb
- value of the peak discharge
- lag time
- time taken to return to normal
